Making of shell bodies



Patented Dec. 14, 1943 UNITED STATES TNT OFHCE No Drawing. Application July 16, 1940, Serial No. 345,811

1 Claim.

This invention relates to a method of manufacturing forged shell bodies for high explosive shells. and constitutes an improvement on my application Serial No. 312,499, filed January 5, 1940, which has matured into Patent No. 2,251,- 094, of July 29, 1941.

In the aforesaid application I propose to produce a blank to form a slug, and subsequently cross roll the blank into a shell body of approximate final dimensions and contour. The slug, which may be cut oif from round, square or polygonal stock, is first subjected to a centering operation with a punch, which serves to fill the die and at the same time to form a centering cavity in one face. The second operation is to pierce the blank thus produced with a piercing punch and die producing the closed-end blank which is subsequently to be cross rolled. This blank is relatively short in length compared to the length of the shell body to be ultimately produced, i. e., it is substantially larger in diameter'and shorter in length. In fact, the bore of the blank is advantageously greater in diameter than the bore of the finished shell body. In consequence, the stroke of the centering punch is very short, as is the stroke of the piercing punch, whereby the power requirements are substantially reduced. Moreover, since the stroke is short and the diameter of the piercing punch relatively large, eccentricity between the bore and the outside periphery of the body is greatly minimized if not eliminated. By reason of the fact that the diameter of the piercing punch is relatively large, punch maintenance is greatly reduced as the punch can be permitted to wear to a considerable extent before it is necessary to replace it. Piercing punch maintenance costs are further reduced by reason of the fact that surface imperfections in the punch present no difiiculty, at least until the time when it is necessary to replace the punch.

The next step is to take the relatively thick and short blank thus produced and subject it to cross rolling, as for example in a cross rolling mill such as shown in Assel Patent No. 2,060,- 768, of November 10, 1936. By this cross rolling a substantial reduction in outside diameter is efiected whereby the length needed for the shell body, is gained. This cross rolling is of course done on a, mandrel of the desired finished dimension and contour, the mandrel being suitably supported and guided. By this cross rolling the work is, as it were, ironed in on the mandrel, with the result that the closed-end shell body produced has a bore to finished dimensions and contour. By the cross rolling the outside diameter is also brought down approximately to finished requirements so that no rough machining is required, but on the contrary. only a light finish machining or grinding. Fishtailing is reduced to a minimum as, consequent- 15', is the waste metal. Moreover, if there should be any eccentricity due to poor shop practice in the production of the blank it is for all practical purposes taken care of in the cross rolling. The poundage of the shell body is much less than that of shell bodies produced according to conventional methods, approximately by four pounds for a mm. shell body.

In the process thus far herein generally described and more particularly in the aforesaid application, the desired results can be obtained, but the cost of roll maintenance, control and adjustment in the cross rolling mill is relatively high. There is also a tendency to balloon on occasion.

In accordance with the present invention I have discovered that the foregoing objections are greatly minimized if the cross rolling mill rolls be constructed and adjusted to secure only a rough approximation of the outside diameter of the finished shell body, and if the reduction in the cross rolling mill be followed by a subsequent relatively slight reduction operation which sizes the shell body to a predetermined finished outside diameter such as requires only the light finish machining or commercial grinding heretofore mentioned. This corrects for any ballooning. This subsequent sizing reducing operation may be performed by forcing the shell body on a mandrel, through a ring die, or by passing the shell body, on a mandrel, through a conventional nest of rolls, for example, three or more annularly arranged rolls as shown in Korbuly Patent No. 2,041,937 of 1936. As illustrative of the reduction effected in the second reducing operation, for a 75 mm. shell I prefer to have an outside diameter of the shell body of 3%; inches, which would be reduced in the second operation to 31 3' inches or under.

By this improved process shell bodies can be produced in great number at a relatively low cost compared to the costs of production according to standard methods now in use.

I claim:

The process of producing shell forgings comprising obtaining a closed end blank having a bore of larger diameter than that desired in the finished article, inserting a mandrel having a diameter like that desired in the finished forging in said bore, rolling said blank between cross-rolls to reduce the wall-thickness thereof to a slightly greater thickness than that desired in the finished product and subsequently passing said reduced blank and mandrel through a die to slightly reduce said blank and bring it to the desired diameter and wall-thickness.

CLAUDE A. WITTER. 

